In Mesoamerica and the Andes, the two great empires of the Americas — the Aztecs and Incas — dominated the landscape. Dense populations, productive agriculture, and an aggressive bureaucratic state were the keys to their power. Each had an impressive capital city. Tenochtitlán, established in 1325 at the center of the Aztec Empire, had at its height around 1500 a population of about 250,000, at a time when the European cities of London and Seville each had perhaps 50,000. The Aztec state controlled the fertile valleys in the highlands of Mexico, and Aztec merchants forged trading routes that crisscrossed the empire. Trade, along with tribute demanded from subject peoples (comparable to taxes in Europe), brought gold, textiles, turquoise, obsidian, tropical bird feathers, and cacao to Tenochtitlán. The Europeans who first encountered this city in 1519 marveled at the city’s wealth and beauty. “Some of the soldiers among us who had been in many parts of the world,” wrote Spanish conquistador Bernal Díaz del Castillo, “in Constantinople, and all over Italy, and in Rome, said that [they had never seen] so large a market place and so full of people, and so well regulated and arranged” (American Voices).

Ruled by priests and warrior-nobles, the Aztecs subjugated most of central Mexico. Captured enemies were brought to the capital, where Aztec priests brutally sacrificed thousands of them. The Aztecs believed that these ritual murders sustained the cosmos, ensuring fertile fields and the daily return of the sun.

Cuzco, the Inca capital located more than 11,000 feet above sea level, had perhaps 60,000 residents. A dense network of roads, storehouses, and administrative centers stitched together this improbable high-altitude empire, which ran down the 2,000-mile-long spine of the Andes Mountains. A king claiming divine status ruled the empire through a bureaucracy of nobles. Like the Aztecs, the empire consisted of subordinate kingdoms that had been conquered by the Incas, and tribute flowed from local centers of power to the imperial core.